Conventionally, an air intake control valve including a seal portion that is arranged at an outer peripheral portion of a valve body is known. Such an air intake control valve is disclosed, for example, in JP2010-1847A.
JP2010-1847A discloses an air intake control valve including a valve body in a plate form provided at a boundary of an air intake port relative to a collector (surge tank), and an elastically deformable seal lip (seal portion) disposed at an outer peripheral portion of the valve body for sealing between an inner wall surface of the air intake port and the valve body. The seal lip is formed to extend from the vicinity of an outer peripheral end surface of the valve body in the plate form via a single hinge portion (i.e., a supporting point at the time of elastic deformation) in an opposite direction from a rotation direction of the valve body in a case where the valve body is brought to a closed state. That is, an extending direction of the seal lip that is elastically deformed with reference to the single hinge portion serving as the supporting point at one side in a direction orthogonal to a rotation shaft of the valve body and an extending direction of the seal lip at the other side are opposite from each other. The seal lip is configured to make contact with the inner wall surface of the air intake port by being elastically deformed inwardly with reference to the single hinge portion serving as the supporting point in a case where the valve body is brought to the closed state. In addition, according to the air intake control valve, in the closed state of the valve body, a flow speed of intake air at the intake port side (downstream side) is faster than a flow speed at the collector (surge tank) side (upstream side). Thus, it is considered that a pressure at the downstream side (air intake port side) is lower than a pressure at the upstream side (collector (surge tank) side). In this case, resulting from a pressure difference, the seal lip positioned at each of one side and the other side of the direction orthogonal to the rotation shaft of the valve body is applied with a force towards the air intake port side from the surge tank side of the valve body.